The tricolored plumage patterns known as speckled, mille fleur, porcelain, and spangled (Old English Game type) were studied along with the black and white mottled plumage pattern. Crosses between birds carrying these phenotypes showed the mo gene to be common to all of these plumage color patterns. Crosses between Speckled Sussex and Black-tailed White Japanese Bantams resulted in a new plumage color pattern in which silver replaced gold to change a tricolored to a bicolored pattern. The recessiveness of the mo gene was verified by crossing birds of the wild-type plumage coloration which differed only at the mo locus. Also, a hypothesis for the gene action of mo is offered to account for the many different phenotypes produced by it.